Synchronous telegraph system



NOV'. v W. A. KNOO i SYNGHRONOUS TELEGRAPH SYSTEI I Filed Dec. 4. 1929 2 Sheets-Sheet l W A.- K/vaaP A rroR/vfy Nov. 11551931.

W. A. KNOOP SYNGHRONOUS TELEGRAPH SYSTEM D Filed Dec. 4. 1929 2 Sheets Sheet 2 ArroR/vfy Patented Nov. 17, 1931 y UNITED "s'rA'rEs PATENT oFFl'ca WILLIAI A. INOP, 0I' HEIPBTELD, NEW YORK, ABSIGNOB T0 Bm TELEPHONE LABOBATOBIIB, INCORPORATED,

YORK

I NEW YORK, N. Y., A. COBPOMTION OF NEW mcnnoirous '1.'iimiiaaluur svsrm y Application led December 4, 1929. Serial No. 411,407.

Y This invention relates to synchronous communication systems and articularly to hig'grll speed printing telegrap systems.

'maintain in a positive manner and with exactness, synchrcnism 'between transmitting and receiving apparatus at separated points.

more specific object is to continuously maintain synchronism by causing the receivlo ing apparatus to run as nearly as possible at the same speed as that of associated transmitting apparatus. This is in contrast to systems in which vthe receiver runs at a speed inherently different from 'that of the transmitter and is periodically corrected to synchronism with the transmitter.

A feature of the invention comprises means for the balancing of one against the other and producing a diiferentlal eiect there- 2o from of two portions of a received im ulse which have steep and opposite slopes w ereby a small departure from synchronism will produce a relatively great correcting effect.

The system of the present invention avoids the difliculties inherent in systems lwherein one distributor is run faster or slower than the other and requires constant correction; it avoids the use of mechanical relays as elements of the correction control circuit; and it also renders unnecessar the splitting of im pulses into two parts y pairs of segments connected into two different circuits.

A principle underlying the operation o systems 1n accordance with the presentin- 35 vention is that of selecting from a received impulse (or impulse derived 'from a received impulse) two small parts from regions which r are rapidly and oppositell changing in amplitude and determining t e corrective eiect 1f any by balancing these parts against one another. l

In the drawings, Fig'. 1 shows a signal receiving circuit wherein the correction is effected through the operation of a relay and 45. a differential gear mechanism;

general object of the invention is to impulses are produced in the secondary wind- Fig. 2 illustrates a modification of Fig. 1, wherein the correction is eiected through a vibrating fork;

Fig. 3 shows the signaling current received in the circuit of Fi 2 and the impulses produed thereby on t e correction distributor; an y Fi 4 shows the plate current-grid potential c aracteristic of the vacuum tube amplifier employed in Fig. 2 for impressing voltage impulses 0n the distributor segments.

In Fig. 1 the correction distributor CD, sending distributor SD and receiving distributcr RD are mounted on a common shaft which is driven by a phonic wheel motor DM. Connected between the motor DM and the distributors is a differential gear corrector DGC which is Aadapted to be operated in either direction by another motor M when a loss of synchronism between the distributors shown and those at the distant station (not shown) occurs. The signal waves incomin over line' 10 are repeated through an ampli er 11 and a transformer 12. Voltage ing of transformer 12 and impressed on a circuit extending through continuous ring 13, segmented ring 14 and rotatable brush 15 of distributor CD, a pair of vacuum tube ampliiers 16 and 17 in diierential relation, over conductor 18 and through a vacuum tube rectifier 19. When the plate of rectifier 19 is negative with respect to the filament thereof, no plate current will flow and therefore current will ow through the circuit, just traced, only when impulses of positive polarity are applied to the rectifier. The other end of the transformer 12 is of course negative when the rectifier end'is ositive so' when positive pulses pass throug the rectifier, negative pulses may be impreed on the correcting secments and tubes.

he distributor CD is shown ada ted for twochannels of five impulses each, ut it is understood that a greater number of chan- 90 nels may be employed. The segmented ring comprises alternate live and dead segments. The live segments are alternately interconnected to form two multiples which are respectively connected to the grids of vacuum tubes 16 and 17. When the distributor CD is in synchronism with the transmitting distributor (not shown) at the opposite end of line 10, the rotatable brush 15 will be passing over equal portions of adjacent live segments separated by a dead segment, at the time a signal impulse is being received in the secondary winding of transformer 12. Impulses of only positive polarity flow through rectifier 19 and therefore each positive impulse will be 'equally impressed on the grids of tubes 16 and 17 during the time that brushv 15 is passing over equal portions of the adjacent live segments. The middle portion of the impulse which is of a substantially uniform amplitude, is impressed on the dead segment iii-termediate the two adjacent live segments and therefore only rising and falling end portions of the impulse which have a rapidly varying intensity are impressed on the tubes 16 and 17. The plate circuits of tubes 16 and 17 respectively include two differential windings on a three-position polar relay 20. In normal operation, that is, when the distributors' at opposite ends of line 10 are in synchronism, equal and opposite late currents flow in the two windings of re ay 20 and the armature 21 of the relay remains in a neutral position between contacts 22 and 23. Hence, the armature circuit of motor M, having a field 24 and a source of energizing current 25, is open. The correcting differential gear 26 therefore remains stationary and the distributor continues to rotate at uniform speed. Inductances 27 and 28 are respectively inserted in the plate circuits of tubes 16 and 17 to prevent sudden fluctuation in the plate current and variable resistance 29 is inserted in the vlate circuit of one of the tubes to equalize t e normal currents through the differential windings of relay 20 in case the characteristics of tubes 16 and 17 should differ slightly from each other. Connected in parallel with the grids of tubes 16 and 17 are shunted condensers 30 and "31 whereby the voltages impressed onthe grids may be prolonged sufiiciently to be effective in the windings of relay 20. The plate battery for tubes 16 and 17 is connected to the differential windings of relay 20 through a differential ammeter 32.

If a departure from synchronism occurs, the distributor brush 15 will lag or lead the received signals and the unequal synchronizing impulses will be applied to the grids of tubes 16 and 17 Therefore unequal currents will flow in the two windings of relay 20 and the relay armature 21 will o erate to either of contacts 22 and 23 de en ing on whether the distributor brush is agging or leading the incomin signals. This causes current to pass throug the armature of motor M, of such a polarity as to cause the motor to shift the distributor brushes, through differential gears 26 in such a direction as to correct for phase displacement. Differential ammeter 32 provides visual means of determining the amount and direction of the departure from synchronism.

In Fig. 2 is shown another embodiment of the present invention wherein the objects of the invention are more effectively attained by eliminating the mechanical relay required .to effect correction as shown in Fig. 1. Fig. 2 therefore shows a continuous correction system whereas Fi 1 shows the step-by-step type of system. n Fig. 2 the correcting distributor CD, sending distributor SD, receiving distributor RD and phonic wheel motor DM are mounted on a common shaft. The correcting distributor comprises a continuous ring 13', a segmented ring 14 and a rotatable brush 15. The segmented ring 14 like ring 14 of Fig. 1 is divided into alternate live and dead segments, the alternate live segments being connected to form two multiples. The incoming signals are received in a pair of transformers 41 and 42 which referably have high permeability cores ci) the type disclosed in copending application of E. T. Burton, Serial N o. 280,709, filed May 26, 1928. These transformers are equipped with core material, such as permalloy, which have a liigh permeability at low magnetizing forces and have a magnetic circuit which becomes overloaded at low voltages of the signaling current. Therefore a signal wave of slowly varying intensities when received in the primary windings produces in the secondary windings, a wave of short, discrete -impulses which occur while the magnetizing force is passing through values slightl above or below zero. By biasing the trans ormersl magnetically in opposite directions the intervals in w ich thek sharp impulses occur are shifted to the higher values of magnetic force so that two impulses are produced during the rise and fall of a signal wave on either the positive or negative side of the zero value. The impulses so produced by each signal wave are of opposite polarity and are produced in one or the other of the. seconda windings depending upon the polarity or Idyirection of the signal wave, that is, those caused by a positive wave are produced in one winding and those caused by a nega-tive wave are roduced in the other winding. The secon ary windings are connected in series, but reversed with respect to each other in order to invert the impulses of one winding, thereby obtaininar a positive impulse at the beginning and a negative impulseat the end of each signal wave regardless of the polarity of the wave. In the embodiment shown herein the impulses of negative polarity are utilized to effect corl vrectioii and the impulses of positive polarity.

lia

are practically eliminated. This is accomlis'hed by connecting a vacuum tube ampli- 121er 43 intermediate the secondary windings of transformers 41 and 42 land correction distributor CD' and by providing in the grid circuit of Vsuch tube a Vhigh' resistance 44. Therefore the voltage dop eiected in the im uls'es of itive polarityis considerable and in such irection as to make the grid of .tube 43 only slightly ositive with respect to the filament, whereas t e voltage drop encoun-` tered by the negative impulses is negligible andthe grid is made negative with respect to the filament. The negative impulse is therefore effective to bloc the space c urrent of tube 43 and to permit the full ositive otential of the plate battery of tu e43 to a plied over the segments of distributor C to the correction circuit to produce the cor-4 rection impulses. The correction impulses are, of course, of positive polarity, there being two for each incoming negative signal impulse.

The two impulses are produced by means of distributor brush 15 in rotating over a group of three segments in the interim in which a negative impulse is being received in the amplifier 43 and the positive potential is being applied to the distributor. The middle segment of the group is dead and therefore when the positive potential is applied the middle portion of the voltage impulse is lost, but the two end portions in which the voltage 1ntensity is changing rapidly, are respectively impressed over the two live segments of the group onto the correction circuit.

When the correcting distributor is in synchronous phase with the transmitting distributor at a distant station (not shown), brush 15 is passing over equal portions of the two live segments separated by a dead segment, at the time an impulse occurs in either of the secondary windings of the transformers, so that each live segment of a v pair receives an equal part of the positive odes of correcting impulse. The equal parts of the positive impulse are respectively impressed through condensers 45 and 46 .onto the antwo vacuum tube rectifiers 47 and 48 as shown, wherein electrons are caused to ow from the cathodes to the anodes and A thence to the lower plates of the condensers.

When the positive charges are removed from the upper plat'es of condensers 45 and 46, the negative charges held on the lower yplates are released and flow through resistl ances :49 and 50 respectively to opposite ,plates of a condenser 51 which acts as a reservoir. i

If the correcting distributor is slightly out of phase with the transmitting distributor, the beginnin and the end of each positive impulse will. e impressed in unequal parts on the anodes of rectiiers 47 and 48 which of short correction impulsesis applied to` one of the tubes 47 an 48, these im ulses will have little or no effect' on the tu s 52 and 53 because of the delaying effect of resistances 49 and 50 and the storage concontinued, though slight,departure from synchronism of the correcting distributor before a correcting tendency is produced.

This tends to stabilize the system and to' prevent obyectionable hunting which might occur if the correction`systein responded to` a single unequal im ulse from the transmittin distributor. which are of high value compared with resistances 49 and 50, provide leak paths for condenser 51. Resistances 56 and 57 which are of relatively low value, provide leak paths for the relatively large capacity condensers 45 and 46.

The plate circuits of ampliers 52 and 53 respectively extend through two windings of a variable reactance coil 58 to a common source of battery supply 59. These windings of the coil are connected in opposite relation so that when the correcting distributor is in phase with the transmitting distributor, any magnetic fields set up by the plate currents of equal value will cancel each other.

The variable reactance coil 58 comprises a core constructed of a magnetic material such as a high permeabilit nickel-iron al-` esistances 54 and 55.

.causing a difdenser 51. In other'words, there must be-a 85 loy, the permeability of w ich varies withthe magnetizin force, and which has a low coercive force 1n order that slight changes in the magnetizing force may roduce corresponding changes in the ux density. The core is magnetically biased from the current source 59 through Winding 60 so that the iiux density is maintained at such a mean average value that small changes in the magnetizing 4force will produce large and approximately proportional changes in the (permeability. In other words, it is desire to work on the steepest part of the permeability curve. The core is equipped with a fourth winding connected .with the circuit extending through a secondary winding 61 on transformer 62 and the winding of magnet 63. This circuit forms a part of a vacuum tube tuning fork circuit arrangement wherein a pick-up ma et 64 is arranged in the magnetic field of t e vibrating fork 65 and adapted to impress the frequency of the fork on a pick-up vacuum tube 66transformer 67, a fork-drive vacuum tube 68 and the primary winding of transformer 62 in series. The output of vacuum tube 68 is ilnpressed on winding 6l of transformer 62 which causes the fork frequency current to flowl through the winding of magnet 63 and the fourth winding of coil 58, the current flowing through magnet 63 being employed to drive the Vibrating fork 65. Another secondary winding 69 of transformer 62 also receives the output of vacuum tube 68 to operate the motor relay 70 where` by phonic lwheel motor DM' is operated to drive the distributors.

The type of variable reactance coil used in the present invention preferably has a shell type core. On the two outside legs is mounted the alternating current winding of the fork-drive circuit and on the middle leg are mounted the two modulating windings of the plate circuits of amplifiers 52 and 53 and the biasing winding 60. With this form of reactance coil, practically no .alternating current is produced in either the biasing or mdulating windings. The alternating current flux circulates around the two outside legs andthe biasing current flux flows from the middle leg and returns through the outside legs in parallel. The biasing current thus saturates the, outside legs and thereby reduces their permeability, and therefore, the reactance of their windings to the alternating current.

When unequal currents, due to correction impulses received when the correcting distributor loses phase, flow in the plate circuits of vacuum tubes 52'and 53, the operating impedance of the coil 58 to the alternating current in the fourth winding is'increased or decreased depending on whether the correcting distributor is going fast or slow. This changes the reactance of the variable reactance coil and in turn changes the power fed to maintain the fork in vibration. This causes the amplitude of vibration of the fork to change and the fork is so adjusted that a change of amplitude causes a change of damping. The damping in turn affects the fork frequency and there is then a corresponding change in the motor speed.

In Fig., 3 is a graphic representation of the operation of transformers 41 and 42 in response to an incoming signal wave illustrated by curve a. The transformers are magnetically biased to be non-responsive to the signal wave until the current reaches values indicated in the drawings by broken lines :v and y. Thus only signal waves above a certain value will be effective to produce vvoltage impulses'in lthe secondary winding. Curve each impulse to produce a b shows two vlt-age impulses produced in the secondary windin every time the signal wave passes t rough the values indicated by broken lines w and narily when the secondary 'win ings are connected in the same direct-ion with respect to eachother, an impulse of positive polarity will be produced with every rise in value of a positive signaland for every drop in value of a negative signal wave, and a negative impulse is produced with every drop in value of the positive signal wave and every rise in value of the negative signal wave, it bein understood, however, that the increases an decreases yin value of the signal wave pass through the values indicated b broken lines and y. But when the secon ary windings of one of the transformers is reversed, as stated above, the -impulses produced in one of the secondary windings will likewise be reversed, such as shown in curve b by t-he impulses designated c which are produced by the negative signal waves shown directly above them. It will be noted that the ositive impulses in curve b are suppresse to an ampplitude where they are hardly discernible.

his is due, as stated above, to the effect of high resistance 44 on the secondary impulses of positive polarity.

Fig. 4 shows the plate current-grid potential characteristic of vacuum tube 43 used in conjunction with high resistance 44, wherein no grid battery is employed and the operating point OP is located approximately at the vmiddle of the straight line portionofthe characteristic. The operating point when so located provides a greater operating range for impulsesl of negative polarity than those of positive polarity.

It is understood that the segments of the correcting distributor may have their lengths chosen in various ways, for example, when the impulse is produced in a secondary winding of a transformer connected to line 10 have sharp peaks, no middle segments are required for the respective groups of segments, but when the 'impulses are ilatat the top the middle segments are employed,I their lengths being directly proportit nal to the lengths of the flat-topped portions.

It is also understood that the correction circuit of Fig. 2 shown below'and to the right of dotted line AB may be substituted for that part of the circuit of Fig. 1 shown below and to the right of dotted line A-B, and vice versa.

lVhat is claimed is:

1. The method of causing a synchronous device to remain closely in phase with another synchronous device by means of a series of impulses over a circuit, which comprises suppressing a portion of each impulse and selecting the rapidly chan ing portions of plurality of pulses Ordiof one polarity, and impressing said pluralityl of pulses on a luralit of ot er circuits arranged in di erentia relation with each other for maintaining the desired phase relal plitudes of the selected portions is effective to accelerate or decelerate said driving'means.

3. A s stem for synchronizing a periodic device with a series of incoming current impulses which comprises instrumentalities for producing in response to the incoming current of varying values, volta e `impulses of one polarity, each of said vo tage impulses being eiective to produce a plurality of correcting pulses o the same polarit and means including correcting circuits w ereby each of said correcting pulses produces an l eiect upon said circuits which is nil,.accele'r atory or deceleratory in a manner proportional to and dependent u on the phase relation of said devicewith respect to said produced impulses.

4. In a telegraph system, synchronizing means comprisino means for producingsynchronizing impu ses of constant polarity from received signal impulses, a rotary dis- .tributor comprising a ring of alternate live and dead segments, means for causing said synchronizing impulses to correct for de-- partures from synchronism of said rotary distributor characterized in this, that it comprises two three-electrode vacuum tubes with their input circuits respectively connected to alternate live' segments of said rotary distributor, to which said synchronizing impulses are alpplied, and with their output circuits inclu ing differential windings of an electromagnetic device, and meansv for driving said distributor, the speed of which is responsive to the flux in said electromagnetic device produced by the difference of the currents in said differential windings.

5. In a synchronizing system, a source of synchronizing impulses of constant polarity, a synchronous distributor, electromagnetic means comprising two mutually inductive diierential windings, contacting means on said distributor for applying a plurality ofl correction pulsesI from portions oi but not the whole of each synchronizing impulse equally or unequally to said diierential windings depending on the phase of the distributor relative to the phase of the synchro- `nizi'ng impulses, and means associated with controlled by the selectrents in said windings to retard or advance the s d of said distributor.

6. a synchronizing system, a source of synchronizing impulses'of constant polarity, a 0iyrichronous distributor, two three-electr e vacuum tubes having 'input circuits and output circuits, electroma etic means comprising two mutually in uctive differential windin each of said windin bein connected in the out ut circuit o one o said tubes, means on said distributor for ap lying' a lurality of correcting pulses of te one po arity from the beginning and end of but not the middle of eac of said synchronizing impulses equally or unequally to the input circuits of said tubes depending on the phase of the. distributor relative to that of the synchronizing impulses, and means associated with said electromagnetic means and with said'rotary distributor responsive to unequal current in said windings to retard or advance said distributor.

7 In a synchronizing system according to claim 6, the input circuit of each of said 'vacuum tubes comprises a condenser in the` grid lead anda leak resistance between the grid and cathode.

8. In a' synchronizing system, a sourceof synchronizing impulses of constant polarity, synchronous distributin means comprising alternate live and dea contacts, two conductors arranged to be respectively lconnected in repeated rotation to the alternate live contacts', a condenser connected to each conductor, electromagnetic means comprising two mutually inductive dierential windings, a source of otential, two `vacuum tubes each having a p ate connected through one of said differential windings and said source of potential to its cathode and having the grid connected to one of said conductors on said synchronous distributor, a resistance con- 'nected between the grid and cathode of each tube, a second resistance connected between each conductor and the cathode of one tube,

a connection between the cathode of each tube and one terminal of said source of synchronizmg impulses and a connection between the other terminal and the contact of said\ synchronous distributing means and means associated with said electromagnetic means and with said distributing means responsive to unequal currents in said differential windings to retard or advance the speed of said distributing means.

9. A system for synchronizing an oscillatory device with a series of incoming current impulses which comprises instrumentalities for producing in response to the incoming impulses of one plolarity voltage impulses of one polarit t e be in and end of but not the mi dle of eac of said voltage impulses being eiective to produce a plurality of correcting pulses of the same polarit and means for applying said correctin p to circuits including two diiferenti'ay related vacuumltube elements connected to a ma netic core whereby the inductance of said core is controlled by the di'erence of thev effects produced on said elements by said correcting pulses, and connections between said device and said core whereby the variation of magnetic condition of said core controls said device in a continuously proportional manner.

In witness whereof, I hereunto subscribe my name this 3 da of December, 1929.

. WLLIAM A. KNOOP. 

